Most electrostatic printing apparatuses use dry toners for text and image printing. The quality and clarity of the text and image is related to the toner particle size. While very fine particle size can be achieved, environmental concerns limit the degree of minuteness that can be used in the toner particle size. In fixing the image, the dry toner particles are fused onto the printing media (e.g. paper) at relatively high temperature (e.g. in excess of about 100° C.). The high temperature of the fuser roll limits the printing speed and image quality of the printing apparatus. When the printing speed is increased, the dwelling time for the toner particles on the fuser roll is shortened. Short dwelling time of toner particles on the fuser roll (fast printing) often results in poor toner adhesion on the paper. To overcome this mentioned disadvantage, liquid toner has been developed for electrostatic printing.
In liquid toner, the toner particles are dispersed in a carrier liquid. Very fine toner particles can be used in the liquid toner without the same environmental concerns that arise with dry toner. Furthermore, high temperature is not needed to fuse the toner to paper. These advantages of liquid toner enable the printing apparatus to print high quality image at high speed. The Indigo® printing press from Hewlett-Packard applies liquid toner (Electroink®) technology to print high quality images. Paper is widely used as the image receiving media with the Indigo® press.